1. Field of the Invention
This invention pertains generally to communication networks, and more particularly to systems and methods calculating distance vectors between wireless network devices.
2. Description of Related Art
The Open System Interconnection (OSI) standard provides a seven layered hierarchy between an end user and a physical device through which various network systems can communicate. Each layer is responsible for different tasks and the OSI protocol specifies the interaction between layers while ensuring that the communication devices comply with the standard.
FIG. 1 shows the hierarchy 100 of the seven-layered OSI standard, which includes a physical layer 105, a data link layer 110, a network layer 115, a transport layer 120, a session layer 125, a presentation layer 130 and an application layer 135.
The physical layer 105 conveys the bit stream through the network at the electrical, mechanical and functional level, while providing a hardware means of sending and receiving data on a carrier. The data link layer 110 provides the representation of bits on the physical medium and the format of messages on the physical medium, sending blocks of data, such as frames, with proper synchronization. The networking layer 115 handles the routing and forwarding of the data to proper destinations, while maintaining and terminating connections. The transport layer 120 manages the end-to-end control and error checking to ensure complete data transfer. The session layer 125 sets up coordinates, and terminates communications between applications. The presentation layer 130 converts incoming and outgoing data from one presentation format to another. The applications layer 135 is where communications, quality of service, user authentication, and so forth are considered.
Similar to the OSI standard, the IEEE 802 committee has developed a three layer architecture for wireless networks that roughly corresponds to the physical layer and data link layer of the OSI standard. FIG. 2 illustrates the IEEE 802 standard 160. As shown in FIG. 2, the IEEE 802 standard includes a physical layer 165, a media access control (MAC) layer 170, and a logical link control layer 175. The physical layer 165 operates similar to the physical layer in the OSI standard. The MAC and the logical link control layers share the functions of the data link layer in the OSI standard 100. The logical link control layer 175 places data into frames that can communicate at the physical layer 165 and the MAC layer 170 manages communications over the data link sending data frames and receiving acknowledgment (ACK) frames.
Together the MAC layer 170 and the link control layer 175 are responsible for error checking as well as retransmission of frames that are not received and acknowledged.
The IEEE 802.11 standard also defines beacon frames within the MAC layer which are sent at regular intervals by an access point. The access point may act as a bridge between two networks with different protocols (e.g., Ethernet and IEEE 802 wireless networks).
Wireless technologies have been integrated into our daily lives and are being required to provide not only connectivity, but also high performance, reliability and stable communication. The most dominant of the IEEE 802 wireless communication standards is IEEE 802.11 and its variants, such as 802.11a, 802.11b, 802.11g which are being utilized in various wireless products. Communication between different devices (nodes) in the IEEE 802 network is performed by the exchanging of data frames between a sending node and a receiving node. Each IEEE 802.11b frame transmitted from a IEEE 802.11 equipped device contains information including the signal strength and noise. By measuring the signal strength information and including it in frames sent from a fixed node to a mobile node, it is possible to approximate the distance between fixed and mobile nodes.
However, it is very difficult to determine the exact location of a node at any point in time, because IEEE 802.11b is very susceptible to the effects of multipath fading, a multipath scenario illustrated in FIG. 2. As shown in the figure, a transmission emitting from a base station 220 is transmitted by an antenna 210. The transmission may take a direct path to a receiving mobile node 230 or, given the physical surroundings, the transmission may radiate, reflect or be diffused by one or more objects 240 and 250 that are closer to antenna 210. This causes a multipath propagation of the signal directed towards the receiving device 230.
Similarly, in a mobile wireless network system, such as a home wireless network, the occurrence of multipath propagation may cause the perceived signal strength information at one wireless network communication device to fluctuate greatly as a result of the slightest movement of the node or changes in the surroundings such as movement of obstacles in the line of sight. The fluctuation in signal strength makes it difficult to determine the location of one wireless network communication device relative to the other wireless devices in the wireless network.
Furthermore, the inability to accurately monitor movements of the different wireless network devices within the wireless network, sometimes impacts the ability to detect the addition or removal of a wireless network device from the wireless network.
Therefore, a need exists to monitor the signal strength between mobile wireless network devices communicating over a wireless network in order to determine the relative proximity and/or motion with respect to other wireless devices on the wireless network. The present invention fulfills that need as well as others and overcomes many of the deficiencies of prior network systems.